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Rule Reference

SEC314lintai-ai-securitystabletool_jsonwarn

Tool descriptor: missing machine fields

MCP-style tool descriptor is missing required machine fields

Provider
lintai-ai-security
Surface
tool_json
Scope
per_file
Tier
stable
Severity
warn
Confidence
high
Detection
structural
Remediation
message_only

Activation Model

Preset Membership

This rule is part of the builtin activation graph through these preset memberships.

basemembership
mcpmembership

Lifecycle

Stable Lifecycle Contract

State

stable_gated

Graduation rationale

Checks unambiguous MCP-style tool descriptors for missing machine fields instead of relying on prose heuristics.

Deterministic signal basis

ToolJsonSignals MCP collection analysis over parsed tool descriptor JSON.

Malicious corpus
tool-json-mcp-missing-machine-fields
Benign corpus
tool-json-mcp-valid-tool
structured evidence required remediation reviewed
Canonical note

Structural stable rule intended as a high-precision check with deterministic evidence.

Nearby Signals

Related Rules

SEC315Tool descriptors: duplicate tool namesMCP-style tool descriptor collection contains duplicate tool namestool_jsonstable
SEC316OpenAI strict schema: missing additionalProperties falseOpenAI strict tool schema omits recursive additionalProperties: falsetool_jsonstable
SEC317OpenAI strict schema: properties not all requiredOpenAI strict tool schema does not require every declared propertytool_jsonstable
SEC318Anthropic strict schema: missing additionalProperties falseAnthropic strict tool input schema omits additionalProperties: falsetool_jsonstable

Why It Matters ​

Tool descriptors are machine-consumed contracts. If required machine fields are missing, downstream MCP-style loaders can interpret the tool inconsistently or fail outright.

What Triggers ​

SEC314 applies to unambiguous MCP-style tool descriptor collections and triggers when a tool entry is missing required machine-facing fields.

Example that triggers:

json
[
  {
    "name": "list_clusters",
    "description": "List clusters"
  }
]

Example that stays clean:

json
{
  "name": "cloudbase-mcp",
  "tools": [
    {
      "name": "auth",
      "inputSchema": { "type": "object", "properties": {}, "additionalProperties": false }
    }
  ]
}

False Positives ​

The rule is structural and only applies when the JSON clearly looks like an MCP-style tool descriptor surface. Wrapper documents that are not themselves raw tool collections stay clean.

Remediation ​

Add the missing machine field so the exported tool remains explicit and deterministic for downstream loaders.